The nonvolatile semiconductor memory devices represented by a flash memory have been widely used as high-capacity and small-scale information recording media in various fields such as computers, communication systems, measuring devices, automatic control devices, and everyday device used around individuals, and there is a great demand for a more inexpensive and high-capacity nonvolatile semiconductor memory device. It is because, since a writing can be electrically performed and data is not erased even after turning off a power supply, the nonvolatile semiconductor memory device is expected to fulfill its function in memory cards and cellular phones that are easily carried and data storages and program storages for storing data in a nonvolatile manner as initial setting to run devices.
Meanwhile, in view of the recent situation that application programs and data itself tend to expand, a system is required to enable software stored in the flash memory to be written, a bug to be fixed, and a function to be upgraded, for the future. However, according to the flash memory that represents the conventional nonvolatile semiconductor memory devices, it takes very long time to write data, and it is necessary to ensure an extra storage region to buffer a file because there is a limit to data amount that can be written at one time, so that the problem is that the process procedure becomes very complicated at the time of writing.
In addition, since it is estimated that there is a limit to miniaturization of the flash memory in principle, new type nonvolatile semiconductor memory devices to replace the flash memory have been widely studied recently. Among them, research and development have been increasingly carried out regarding a resistance-change type nonvolatile semiconductor memory device using a phenomenon in which resistance is changed by applying a voltage to a metal oxide film, because this nonvolatile semiconductor memory device has the advantage over the flash memory in view of miniaturization limit and can write data at high speed.
The phenomenon itself in which the resistance is changed by applying the voltage to the metal oxide such as nickel, iron, copper, and titanium has been studied since 1960s (refer to a non-patent document 1), but it was not put to practical use in an actual device at that time. In the late 1990s, it was proposed to use the phenomenon in which by applying a voltage pulse to manganese or copper oxide having a Perovskite structure for a short time, material deterioration can be minimally-suppressed, and the resistance can be irreversibly increased or decreased, and to apply the phenomenon to the nonvolatile semiconductor memory device, and then, it has been verified that a memory cell array composed of memory unit elements (memory cells) made by combining the variable resistance element made from these metal oxides with a transistor or a diode can be formed on a semiconductor chip actually, which was reported in IEDM (International Electron Device Meeting) in 2002 (refer to a non-patent document 2), so that studies have been extensively conducted in a semiconductor industry since then. After that, it has been reported that nickel or copper oxide studied in 1960s is also combined with the transistor or the diode based on the similar idea (refer to a non-patent document 3 and a non-patent document 4).
These techniques can be regarded as the same technique basically because they all use the resistance change of the metal oxide caused by the application of the voltage pulse, and use the different resistance states as memory information of the nonvolatile semiconductor memory device (memory element therein).
The variable resistance element (resistance element made from metal oxide) whose resistance is changed by the voltage application shows various resistance characteristics and resistance change characteristics depending on used materials of metal oxide (the metal oxide whose resistance value is changed by the voltage application is referred to as the “variable resistor” hereinafter), electrode materials, and shapes, sizes, and action conditions of the element. However, the factor of the diversity of the characteristics is not clear. That is, the researcher regards an action condition showing the best characteristic as the memory element composing the nonvolatile semiconductor memory device (referred to as the “nonvolatile semiconductor memory device element” hereinafter) made by chance, as the action condition of the element, and the entire picture of these characteristics are not sufficiently understood, and the situation in which there is no unified design guide has been continued up to the present.
The situation in which there is no unified design guide means that the variable resistance element does not reach the true meaning of industrially available technique. In other words, although the variable resistance element provided based on the above empirically optimized technique can be used as a single nonvolatile semiconductor memory device or as a component made by integrating the memory elements on a small scale, it cannot be applied to the present semiconductor memory device requiring the quality assurance of large scale and high integration of one million to one hundred million or more like the flash memory.
One specific example of the situation in which the entire picture is not grasped is the control of the element resistance of the variable resistance element. Although the switching characteristics in various element materials have been reported to the present, most of them just describe the characteristic of the produced memory element. As for the control of a resistance value, there are disclosed a method of controlling a current after programming by comparing a current value flowing at the time of programming with a reference current value and cutting voltage application when the current value exceeds the reference current value (refer to a patent document 1, for example), and a method of controlling the a current amount flowing in a variable resistance element by changing a voltage applied to a gate electrode of a selection transistor at the time of programming or erasing, in a nonvolatile semiconductor memory device having a memory cell composed of the selection transistor and the variable resistance element (refer to a patent document 2, for example).
Patent document 1: Japanese Unexamined Patent Publication No. 2006-135335
Patent document 2: Japanese Unexamined Patent Publication No. 2005-25914
Non-patent document 1: H. Pagnia et al., “Bistable Switching in Electroformed Metal-Insulator-Metal Devices”, Physica Status Solidi (a), 108, pp. 11-65, 1988
Non-patent document 2: W. W. Zhuang et al., “Novell Colossal Magnetoresistive Thin Film Nonvolatile Resistance Random Access Memory (RRAM)”, IEDM Technical Digest, pp. 193-196, 2002. 12
Non-patent document 3: I. G. Beak et al., “Highly Scalable Non-Volatile Resistive Memory Using Simple Binary Oxide Driven By Asymmetricunipolar Voltage Pulses”, IEDM, 2004
Non-patent document 4: A. Chen et al, “Non-Volatile Resistive Switching For Advanced Memory Applications”, IEDM, 2005